What is an anchor bolt and its application?

A crucial part of construction, anchor bolts are used to fasten structures or objects to concrete. Usually, these bolts feature a threaded end on which washers and nuts can be fastened. Their main purpose is to ensure stability and safety in concrete by offering a strong and reliable fastening.

There are several varieties of anchor bolts, each intended for a particular use. Concrete screws, sleeve anchors, and wedge anchors are examples of common varieties. The base material (type and thickness of concrete), environmental conditions, and load requirements all play a role in the anchor bolt selection process.

Securing structural components to concrete foundations, such as columns, beams, and equipment, is one of the main uses for anchor bolts. Anchor bolts assist in distributing loads and preventing structural movement or displacement over time by securely fastening these components.

To guarantee the effectiveness of anchor bolt installation, a number of factors must be carefully taken into account. A sturdy and dependable connection can only be made with precise concrete drilling, bolt alignment, and sufficient nut tightening.

What is an anchor bolt for concrete

Many people are aware that problems with fastening to ceilings and the interior and external surfaces of concrete walls can be resolved with the use of a unique fastening element called an anchor bolt. The answer is not universally known. Let’s attempt to define what an anchor is. This metal fastener enables sturdy furniture, equipment, and gadgets to be attached to surfaces made of brick, stone, concrete, foam blocks, hollow panels, and walls composed of gas-filled blocks. A hole with specific dimensions is used to install the fastening element.

An anchor is a fastening tool that is capable of withstanding large forces because of the following:

• frictional forces, due to which the collet sleeve is held in the formed cavity;
• forces of interaction of a special spacer mechanism with the inner surface of the channel;
• adhesive characteristics of the adhesive ingredients located inside the drilled hole.

Concrete expansion anchors and wedge-type anchors are two of the many types of fixing devices that are in great demand. When the fixing element decompresses inside the cavity, its design features and technical parameters enable it to increase the diameter of the working surface. Concurrently, there is a sharp rise in the friction force’s magnitude. An anti-corrosion coating applied to the surface of such an element prolongs its service life by preventing corrosion.

Marking of anchor bolts

If you intend to use concrete anchor bolts, you must learn how to read the markings to determine the dimensions. Let’s use the example of a fastener with the designation M8 10/35×90 to determine how the abbreviation is interpreted:

• The alphanumeric designation M8 indicates the thread diameter;
• The number 10 corresponds to the diameter of the drill for making a cavity in concrete;
• The number 35 indicates the maximum thickness of the attached material;
• The number 90 characterizes the minimum depth of the hole for mounting the anchor.

Selecting fasteners for a particular task is made simple by understanding how anchor bolts are marked.

Anchor bolt – advantages and disadvantages

Every kind of anchor is a universal component that enables fastening in walls composed of different materials. However, it is not economically feasible to use anchors to fasten lightweight objects in wooden walls due to their high cost. The product’s purpose is to guarantee a sturdy connection in materials that are hard to work with, like brick, concrete, and stone.

You can fully enjoy the benefits of specialized fasteners when you use them for what they were designed for:

• increased load-bearing capacity. According to this parameter, the anchor occupies a leading position among other hardware;
• an expanded range of fasteners. It is easy to choose the best option taking into account the installation features;
• use of carbon steel for the manufacture of fasteners. It is resistant to corrosion and is durable;
• easy to perform installation operations. No special equipment is required for fixing, and installation is carried out within a limited time;
• the ability to use anchors to strengthen an existing structure;
• resistance to the effects of forces. The anchor immobility is ensured both in statics and in dynamics with the application of vibration loads.

In addition to the benefits, there are several drawbacks:

• increased cost of products compared to other types of hardware;
• need to pre-make a hole in a solid base;
• selection of the design of the anchor used depending on the base material.

Professional and amateur builders who understand the benefits of using an anchor bolt for concrete have to have one in their toolbox.

What types of anchors are there – classification of fasteners

Anchor bolts of all kinds fall into two categories:

• products with mechanical fixation. Reliable fastening occurs due to friction forces and expanding forces;
• chemical fastening with adhesive composition. It allows fastening in fragile walls made of cellular concrete grades.

Let’s talk more about mechanical fasteners, which are separated into two groups based on the characteristics listed below:

• design variant;
• area of ​​use of products.

Let’s examine the characteristics of each group’s classification.

How metal anchors differ in design

An anchor bolt is a mechanical lock, the working principle of which includes features for various kinds of fasteners. When screwed in, it has the characteristic of increasing transverse size.

Let’s examine the classification of fasteners into types based on design features:

• wedge anchor bolt. It is made in the form of a metal stud with a collet sleeve, which increases in diameter and wedges in the cavity when the rod is screwed in. This is achieved by moving the conical part of the rod inside the spacer sleeve. A nut is screwed onto the threaded part of such an anchor, under which there is a washer. The wedge fastener is installed in a pre-made hole, followed by tightening the nut with an open-end wrench. When the stud moves during screwing, the conical sleeve contacts the collet clamp, which is released and wedged. Such a fastener is capable of withstanding increased loads. However, it creates increased stress in the material over the contact area, which does not allow it to be used in cellular concrete;
• sleeve anchor with nut. Metal sleeve-type anchors are equipped with a locking sleeve, the length of which is equal to the dimensions of the steel rod. A wedge-shaped head is made on the tail part of the stud. When the nut is screwed in, it moves along the threaded part. As a result of the movement, the sleeve is expanded. The design features of this type of fastener allow it to be used in lightweight types of concrete with a cellular structure, as well as in bricks made of fired clay. The possibility of using in brittle materials is associated with the reduced stress that such an anchor creates inside the channel. There are no special requirements for installation work, which allows for through installation. Compared to the wedge, the sleeve retainer has a reduced load capacity;
• collet expansion bolt. The expansion type of fasteners is a modernized version of the sleeve retainer, but has a more complex design. Longitudinal cuts on the expansion sleeve divide its surface into four petals, which, under the influence of the expansion element, partially open, increasing the size of the cross-section. Fixation is ensured both by the forces associated with friction and by changing the shape of the working surface. The load capacity of the expansion element with a collet corresponds to the characteristics of the wedge anchor. The difference is in the reduced stress in the contact zone with the material. The product is used in hollow brick and lightweight types of concrete. The high cost of the anchor limits its wide application;
• drive-in anchor bolt for concrete. The design feature of this retainer is the shape of the inner surface of the expansion sleeve, which is made in the form of a cone with cuts. Inside the sleeve there is a wedge, which, when impacted, moves inside the cavity and expands the sleeve. The drive-in type retainer is designed for installation in concrete structures and solid brick, since high expansion forces are created in the contact zone with the material. Installation is quite simple and quick.

Consideration should be given to an anchor bolt’s design features when choosing one for concrete or another material.

How is a collet bolt classified by area of application

Anchor-style fasteners are employed for repairing:

• window and door frames;
• household electrical equipment;
• staircases;
• suspended ceilings;
• engineering communications;
• steel structures.

Additionally, fasteners are employed for the following uses:

• fixing the metal frame in the foundation;
• ensuring reliable fastening with cellular building materials;
• fastening massive structures to concrete and stone walls;
• remote installation through a thick layer of thermal insulation material or decorative finishing to the facade surface.

You can always select the best kind of fastener for the job.

Anchor bolt sizes for concrete

Depending on the intended use, the threaded part’s diameter and the metal anchors’ length change:

• steel fasteners with metric threads with a diameter of up to 12 mm and a length of no more than 20 cm are used mainly when private owners carry out repair work;
• fasteners with an increased thread diameter of up to 20 mm and a length of up to 35 cm are used for industrial purposes for fixing heavy structures.

The following variables are dependent on the concrete anchor bolt’s dimensions:

• maximum thickness of fixed elements. Depending on the type of fastener, it is 1.5–6 cm;
• maximum size of the bearing surface. It fluctuates between 5 and 30 cm for different types of anchors.

The pull-out load, which ranges from 1.5 to 30 kN, is also influenced by the fasteners’ dimensions and design elements.

Anchor bolts are essential for fastening structures to concrete foundations in the construction industry. Strong grip is provided by the threaded end of these specialized bolts, which are embedded in hardened concrete. Their main use is for attaching structural components to concrete surfaces, such as machinery bases, beams, and columns. Because they keep structures from moving and can withstand forces like wind and seismic loads, anchor bolts are essential for maintaining stability and safety. The longevity and dependability of constructions made of concrete can be considerably increased by knowing their types and proper installation.

Types of wall anchors depending on the fastener material

A metal anchor is composed of sturdy materials and is intended to secure large structures:

• structural steel with a low carbon content. This type of metal provides an increased margin of safety and allows the use of fasteners for increased loads;
• corrosion-resistant steel, which contains alloying elements. Along with an increased margin of safety, the material is resistant to corrosion processes, which allows the use of fasteners in humid conditions;
• aluminum-zinc alloys, which are known as brass. Non-ferrous metal fasteners are used mainly for fastening structures in domestic conditions.

A plastic or polyamide sleeve may be included with some fastener types.

An anchor bolt is an essential building component that is used to firmly secure items to concrete. It has a threaded end on which washers and nuts can be fastened. These bolts are available in a variety of sizes and kinds, each suitable for a particular load capacity and installation need.

Anchor bolts are widely used in construction projects for a variety of purposes, including anchoring machinery and equipment as well as securing structural components like beams and columns. Stability and safety are guaranteed by their sturdy design, which is essential in settings where structural integrity is crucial.

To ensure the effectiveness of anchor bolts, proper installation techniques are necessary. This entails drilling holes in the concrete precisely, selecting anchors that are suitable for the load, and tightening them to the advised torque specifications. By paying close attention to these details, failure risks are reduced and the bolts’ holding power is increased.

The type of concrete being used, the load it will support, and other factors all play a role in selecting the appropriate anchor bolt. Among the popular varieties are concrete screws, sleeve anchors, and wedge anchors; each has a unique benefit depending on load-bearing capability, ease of installation, and adaptability.

Video on the topic

Anchor bolt, anchor bolt with nut, frame dowel (frame anchor)

Anchor bolt. Installation, operating principle.

WHAT IS AN ANCHOR BOLT – OPERATING PRINCIPLE ✔ Watch and learn!